Subheadings

Subheadings enable your readers to
find
detailed information quickly. They also give the reader an idea of how
deeply a topic is covered.

Subheadings provide more detail
about
the topic stated in the main entry. Effective subheadings represent
distinct
aspects of a topic. The following example, from Beyond Public
Architecture:
Strategies for Design Evaluations, includes the city with each
subheading.
Ideally, each subheading has only one or two page references:

Sometimes a topic, or main
heading, can
be divided into sub-classifications. For example, vehicles could be
subdivided
into “types of” vehicles such automobiles, trucks and buses. Similarly,
a house could be subdivided into “parts of” the house such as walls,
rooms,
roof, plumbing, etc.

Sub-classifications of a main
heading
make poor subheadings because they do not tell the reader more “about”
the topic. Ideally, a sub-classification should be raised to a main
heading
with a “See also” cross-reference from the original main topic. In the
following example, from Concepts of Mass in Contemporary Physics
and
Philosophy, the main heading “general relativity” makes a “See
also”
cross-reference to two sub-classifications, “relativity, Einstein's
theory
of” and “special relativity”: